Bone diseases Flashcards
Achondroplasia: what is it?
Failure of longitudinal bone growth -> short limbs
Achondroplasia: what kind of ossification is affected, and which is not affected?
Endochondral ossification is affected -> short limbs
Membranous ossification intact -> relatively big head
Achondroplasia: which protein is affected? Which cells are affected?
Constitutive activation of Fibroblast growth factor receptor 3 (FGFR3) -> inhibits chondrocytes proliferation
Achondroplasia: what percentage of mutations occur sporadically (during spermatogenesis?
85%
Achrondroplasia: genetics?
Autosomal dominant with full penetrance (homozygoty is lethal)
85% of mutations occur sporadically
Achondroplasia: risk factor?
High paternal age
What is the most common cause of short-limbed dwarfism?
Achrondroplasia
Osteoporosis: what is it?
Loss of bone mass, both cortical and trabecular, despite normal bone mineralization and lab values
Osteoporosis: lab values of calcium and phosphate?
Normal
Osteoporosis: most common cause?
Low estrogen levels and old age: increased bone resorption
Osteoporosis: can be secondary to which conditions?
Hyperparathyreodism
Hyperthyreodism
Multiple myeloma
Malabsorption syndromes
Anorexia
Osteoporosis: can be secondary to which medications?
Steroids
Alcohol
Anticonvulsants
Anticoagulants
Thyroid replacement therapy
Osteoporosis: how to diagnose?
DEXA-scan (lumbar spine, total hip and femoral neck with a T-score of -2.5)
OR
Fragility fracture (fall from standing height, minimal trauma)
Osteoporosis: when to screen?
1x in females >65
Osteoporosis: prophylaxis?
Regular weight bearing exercise, adequate calcium and vit D intake throughout adulthood
Osteoporosis: DEXA of what and which values?
Lumbar spine, total hip, femoral neck. T-score <2.5
Osteoporosis: treatment?
Biphosphonate
Other:
- Teriparatide (synthetic PTH, promotes osteoblast survival)
- SERM (selective estrogen receptor modulators)
- Rarely calcitonin, denosumab (monoclonal antibody against RANKL)
Osteoporosis: complication?
Vertebral compression fracture: acute back pain, loss of height, kyphosis
Can also present with fractures of femoral neck and distal radius
What is a fracture of the distal radius?
Colles fracture
Colles fracture
Fracture of distal radius
What is loss of bone mass with normal mineralization and lab values?
Osteoporosis
Osteopetrosis: what is it?
Failure of bone resorption -> thickened dense bones that are prone to fracture
Osteopetrosis: which cells are defective?
Osteoclasts (failure of bone resorption)
Osteopetrosis: underlying pathophysiology
Mutations impair osteoclasts to generate acidic environment
Acidic environment is needed for bone resorption
Osteopetrosis: what happens to the bone marrow?
Overgrowth of bone fills marrow space -> pancytopenia, extremedullary hematopoiesis
Osteopetrosis: lab values of blood cells?
Pancytopenia
Osteopetrosis: complication?
Cranial nerve impingement and palsies due to narrowed foramina